This invention relates to improvements in the mounting and alignment of saws and is particularly applicable to circular saws used for cutting a workpiece.
In order to guide a saw blade rotating about a drive axis, the drive for the saw blade is usually mounted to a frame having a blade guard. A reference for the cutting plane of the rotating saw blade is provided by a base plate affixed to the frame through which the saw blade projects. The base plate which usually slides on its flat surface across a workpiece defines the angle of the cutting plane to the workpiece by the relative position of the cutting blade to the base plate. Hence the angle of the cutting blade is best varied by changing the angle of the cutting plane relative to the base plate. This generally occurs by pivoting the cutting plane about an axis parallel to that plane.
The depth of the cut from the cutting blade is determined by the distance below the base plate through which the blade extends. This depth is adjusted by altering the position of the base plate relative to the frame. The most common form of adjustment is simply by pivoting the frame about an axis on the base plate parallel to the drive axis of the cutting blade, thereby, in effect raising or lowering the blade relative to the base plate.
In the case of most circular saws, the adjustment mechanisms which allow adjustment of the angle of the cutting blade provide for only coarse adjustment. Consequently, precise cutting and fine adjustment of the angle and depth of a cut is difficult.
It is an object of the present invention to provide a circular saw which overcomes at least one of the adjustment problems outlined above.
Accordingly, the invention is applicable to a saw including a frame, a drive means mounted to the frame coupled to a planar saw blade for rotation about a drive axis within a cutting plane and a base pivotally mounted to the frame about a first axis substantially parallel to the cutting plane and a second axis which is generally substantially parallel to the drive axis. Conventionally the first a xis corresponds with the longitudinal axis of the saw and the second axis corresponds with the transverse axis.
In a first aspect of the invention, the pivotal movement of the frame about the second pivotal axis is determined by a mounting assembly, the mounting assembly providing a means of course adjustment of the position of the base relative to the frame and a means of fine adjustment of the position of the base relative to the frame. The mounting assembly may include a sliding height bracket and adjustably engaging the frame to provide course adjustment of the base relative to the frame and an attachment bracket engaging the frame and adjustably engaging the sliding height bracket to provide fine adjustment of the base relative to the frame. To provide fine adjustment of the position of the base relative to the frame, the attachment bracket of the mounting assembly adjustably engages the sliding height bracket. Adjustment of the position of the sliding height bracket relative to the attachment bracket by a fine adjustment mechanism provides fine adjustment of the position of the base relative to the frame.
The applicants have found that by providing a fine adjustment means and a course adjustment means, the depth of saw blade extending below the base plate can be accurately and precisely controlled. The frame is effectively pivotally mounted to the base preferably about pivot mounting which is preferably a forward pivot point and adjustably connected to the base plate at the attachment bracket through the sliding height bracket.
The frame is preferably provided with a protrusion which is slideably received within a slot in the sliding height bracket. A releaseable locking means co-operates with the protrusion to secure the position of the sliding height bracket relative to the frame. It is preferred that the sliding height bracket is further provided with an engagement stud being slidingly received and preferably extending through a guide or slot in the attachment bracket. The position of the stud within the guide of the attachment bracket may be defined by the fine adjustment mechanism. The adjustment mechanism may include a locating rod secured at one end to the engagement stud or bolt of the sliding height bracket, the locating rod preferably being provided with a screw thread. The locating rod preferably extends through a flange on the attachment bracket and is held in position by a threaded adjustment knob which abuts against the flange. The position of the sliding height bracket relative to the attachment bracket is thus adjusted by rotation of the threaded adjustment knob which varies the extension of the locating rod through the flange on the attachment bracket.
In a second preferred aspect of the invention, there is provided a saw including a frame, a drive means mounted to the frame coupled to a planar saw blade for rotation about a drive axis within a cutting plane and a base pivotally mounted to the frame about a first axis substantially parallel to the cutting plane and a second axis which is generally substantially parallel to the drive axis, wherein the pivotal movement of the frame about the second pivotal axis is determined by a mounting assembly, the mounting assembly providing a means of course adjustment of the position of the base relative to the frame and a means of fine adjustment of the position of the base relative to the frame.
The provision of a position locator allows the trim of the rotating saw blade as determined by the angle of the base plate relative to the frame to be set in one of a number predetermined discrete settings when the locator is engaged. By providing a disengaging function on the discrete position locator, the angle of the base plate relative to the frame can alternatively be set at any angle over a continuous range of angles by the locking means when the locator is disengaged.
The first pivot axis of the frame about the base is defined by a first pivot mounting on the frame and the second pivot mounting on the base, the pivotal angle being set by the trim adjuster. The position locator of the trim adjuster includes a pawl housing and a slotted cover plate, the pawl housing preferably secured to the base plate and the slotted cover plate to the front pivot bracket of the frame. The slot in the cover plate may be provided with a plurality of notches for receiving a pawl pivotable within the pawl housing between an engaged and a disengaged position.
To adjust and set a predetermined angle of the base plate relative to the cutting plane, the pawl is disengaged and the cover plate rotated relative to the housing. When the desired preset angle between the base plate and frame is reached, the pawl engages the corresponding preset notch in the cover plate.
The engagement of the pawl with the preset notch in the cover plate holds the base plate and the frame in position. The position may be further secured by engaging the locking means having ka locking device such as a screw threaded knob or clamp which co-operates with a bolt extending through the slot in the cover plate.
If it is desirable to set the angle between the base plate and the frame at an angle which is not preset as a notch in the coverplate, then the pawl can remain disengaged and the locking means only engaged once the desired angle has been set.
In both cases whether the pawl is engaged or not, a further locking means on the second pivot mounting may be engaged once the angle between the base plate and the frame is set and the forward locking means is secured.
Since the alignment and angle of the frame corresponds with the alignment and angle of the cutting blade, adjustment of the angle of the frame relative to the base plate produces an identical corresponding adjustment of the angle of the cutting blade and cutting plane relative to the base plate. The first pivot mounting is secured to the frame and pivotally mounted to the base plate. The cover plate may be mounted to the first pivot mounting by a fine trim device for limited rotation of the cover plate relative to the first pivot mounting. When the cover plate is secured to the pawl housing either by the engagement of the pawl or the tightening of the locking means, small changes of angle can be effected. Thus small angle variations either side of the preset angles determined by the engagement of the pawl in the notches of the slot of the cover plate may be effected.
The limited pivotal movement of the coverplate relative to the first pivot mounting also enables correction of the pre-set positions of the notches relative to the pawl housing. This limited pivotal movement permits correction of any errors between the indicated angle corresponding to the engagement of the pawl in a notch and the actual angle.
Fine adjustment of the trim angle, ie. the angle of the base plate to the cutting plane is preferably provided by a fine trim device mounted to the first pivot mounting having an eccentrically mounted cam which engages a passage in the cover plate. Rotation of the fine trim device causes limited rotation of the cover plate relative to the first pivot mounting, thereby either varying the position of the cover plate relative to the pawl housing when the pawl is disengaged and the locking means is disengaged, or providing a small variation in the angle between the base plate and the frame when either or both the pawl and the locking means is engaged. In this way, when the pawl is engaged in a notch corresponding to a trim angle of 90xc2x0, angles greater than 90xc2x0 can be obtained by adjustment of the securement device.
This aspect of the invention enables the angle of the base plate relative to the cutting plane to be accurately and positively set. The fine adjustment by limited rotation of the cover plate relative to the first pivot mounting further provides a means to adjust the position of the cover plate and hence the notches relative to the pawl housing and pawl to correct for errors between the actual angle and the angle indicated by the engagement of the pawl in a given notch.
The invention also provides a circular saw having the height adjustment mechanism of the first aspect of the invention and the trim adjustment mechanism of the second aspect of the invention.
Another aspect of the invention relates to positioning a circular saw or other such article beneath a fixture such as a work bench. The preferred use is with a circular saw which is mounted beneath a saw bench with the rotating circular blade extending through a gap or slot in the bench, although this aspect of the invention could equally be applied to mounting any article to a fixture where precise positioning is required.
When used for mounting a circular saw beneath a bench, the blade of the saw extends above the table acting a rip saw for cutting workpieces on the top surface of the work bench. One problem with easily demountable circular saws used in this way has always been precise positioning the rotating cutting blade with respect to the positional fittings on top of the saw bench. The correct positioning is necessary to ensure that the rotating cutting blade is correctly aligned with the direction of any intended cut. This is necessary if only the leading teeth of the saw are to be cutting the workpiece thus providing an unblemished cut.
However, mountings for circular saws and the like articles below work benches generally do not allow precise manoeuvring of the saw within the mountings under the bench. In most cases, the person mounting the saw will not be able to precisely align the blade and therefore will be forced to settle for a very small degree of mis-alignment and the resulting less-than-perfect cut.
Accordingly, in this aspect of the invention relates to a positioning assembly for use with the mountings of an article such as a circular saw to a fixture such as a work bench The assembly includes a plug to be received within an opening in the base of the article, the plug having an adjustment head such as a nut having an axis aligned eccentrically through the plug. The assembly also includes a foot to be received within the mounting on the fixture, the foot engaging the plug through the axis of the adjustable head. The adjustable head is preferably rotatable relative to the foot about the axis of the adjustable head. A shaft preferably extends through the axis of the adjustable head engaging with the foot.
The foot of the positioning assembly in accordance with this aspect of the invention is held in place on the fixture such as a work bench and the base plate of the article such as a circular saw is placed against the fixture with the adjustable head engaging the base plate.
The adjustable head rotated about its axis, due to the eccentric positioning of the axis relative to the adjustable head, alters the alignment of the base plate relative to the mounting bracket of the fixture.
The base plate of the circular saw is preferably provided with two positioning assemblies according to this aspect of the invention. The openings in the base plate for receiving the positioning assemblies are preferably positioned towards the front and rear of the base plate, thereby increasing the possible adjustment to the alignment of the base plate relative to the fixture mountings. This provides adjustment of the alignment of the rotating blade which may extend through a slot or recess in the work bench.